For what if some ( τινες. The expression does net denote whether many or few; it only avoids assertion of universality of unbelief (cf. Romans 11:17; 1 Corinthians 10:7), though it is implied in the following verso that, even if it had been universal, the argument would stand) did not believe?
shall their unbelief make the faith of God without effect? Alford renders ἠπίστησαν "were unfaithful," taking it in the sense of being "unfaithful to the covenant, the very condition of which was to walk in the ways of the Lord, and observe his statutes;" and this on the ground that the apostle is not as yet speaking of faith or the want of it, but, in accordance with the idea of the preceding chapter, of ἀδίκια (Romans 3:5) and moral guilt.
But the meaning of words must not be forced to meet the views of interpreters; and we observe that ἀπιστεῖν and ἀπιστία are ever elsewhere used in their proper sense to denote want of faith. Still, it is to be observed that in the passage before us ἀπιστία in man is opposed to πίστις in God, so as to suggest a more general sense of ἀπιστία than mere unbelief.
In view of this opposition, we may adopt the rendering of the whole passage in the Revised Version: "What if some were without faith? Shall their want of faith," etc.? Meyer and others, understanding (as said above) by λόγια the Divine oracles which were prophetic of Christ, refer ἠπίστησαν exclusively to the disbelief in him on the part of the majority of the Jews at the time of writing.
But the aorist tense of the verb, as well as the context, is against the idea of such reference, at any rate exclusively. The context, both in Romans 2:1-29. and the latter part of this chapter after Romans 2:9, certainly suggests rather reference to the failure of the Jews throughout their history to realize the advantage of their privileged position; and this failure might properly be attributed to their want of faith, to the καρτδία πονηρὰ ἀπιστίας (Hebrews 3:12), cf.
Hebrews 3:19; Hebrews 4:2, together with Romans 4:11. ἀπιστία in these passages is regarded as the root of ἀπειθεία. On the other hand, the whole drift of Romans 11:1-36. in this Epistle—where the present ἀπιστία of the chosen people shown in their rejection of the gospel is spoken of as not hindering, but furthering, the righteous purpose of God, and redounding in the end to his glory—suggests a like reference here.
And it may have been in the apostle's mind, though, for the reasons above given, it can hardly be the only one in the passage before us.